Firefighters who responded to World Trade Center attacks more likely to have cancer than others, study suggests 2:46

Firefighters who responded to the 9/11 attacks at the World Trade Center are more likely to have cancer than their colleagues who were not exposed, a new study suggests.

Thursday's issue of the medical journal The Lancet is devoted to the 10th anniversary of the Sept. 11, 2001, attacks on the U.S.

Firefighters who worked at Ground Zero were up to 19 per cent more likely to have cancer than other firefighters, Dr. David Prezant, chief medical officer of New York City's fire department and his co-authors found in the study of nearly 10,000 male firefighters.

"Nineteen per cent more likely, and that represents an astonishing concept only seven years after 9/11," Prezant said in an interview.

For the study, Prezant and his team compared cancer incidence rates among firefighters exposed at the World Trade Center (WTC) with cancer incidence in non-exposed firefighters and reference rates from the U.S. National Cancer Institute. Factors such as age and race were taken into account.

During the study, the researchers found 263 cases of cancer occurred compared with 238 expected from the general population. Among firefighters who did not work at the site, 135 cancers were diagnosed compared with 161 expected from the general population.

Firefighter John McNamara, 41, was one of about 12,500 first responders who went to the WTC.

"In 2006, when I was actually four months pregnant with my son, [John] was diagnosed with stage four colon cancer," recalled Jennifer McNamara of Long Island, N.Y.

McNamara's cancer spread to his stomach and liver. He died 3½ years later.

"It was such an incredibly aggressive cancer, and if you have no genetic predisposition, it is clearly going to have to be environmental," his widow said. "And what is the big environmental disaster lurking in our background, it's 9/11. He had no doubt and I have no doubt that's what it was."

Respiratory illnesses have been recognized as being the result of exposures after the attack but cancer has not.

"If you were to ask me in my gut do I think there is going to be a link over time, I think there will be an association between World Trade Center exposures," said Dr. Jacqueline Moline, chair of population health at North Shore University Hospital in New York, who has investigated cases of multiple myeloma in first responders. "That's not proven yet."

Proving any cancer link will take time because cancers generally take many years to develop, Moline said.

Cancer and debris

Only some of the first responders who went to WTC had respirators. During the first days, no one measured or tracked what was in the dust they breathed, which included chemicals that are known to cause cancer.

"An association between WTC exposure and cancer is biologically plausible, because some contaminants in the WTC dust, such as polycyclic aromatic hydrocarbons, polychlorinated biphenyls, and dioxins, are known carcinogens," Prezant and his co-authors wrote.

They said the findings support continued monitoring of firefighters and others exposed on 9/11 to fully assess cancer risk.

Besides causing cancer directly, working at the World Trade Center could also trigger chronic inflammation, through microbial infections, autoimmune diseases, or other inflammatory disorders, all of which are thought to contribute to causing cancer, the investigators said.

It is biologically plausible that the exposure would cause cancer over time, Moline said.

"The findings from the accompanying study show an increased overall cancer risk in these WTC-exposed firefighters, and significantly raised cancer risk at a few specific sites (i.e. melanoma, thyroid, prostate, and non-Hodgkin lymphoma) compared with the general population," James Melius of the NYS Laborers' Health Fund in Albany, N.Y., said in a journal commentary accompanying the latest research.

Waiting until definitive cancer studies are done would pose a hardship for workers who risked their health by responding, said Melius, who works for a joint labour-management fund that represents many of the workers at the WTC site.

Prezant's study was funded by the U.S. National Institute for Occupational Safety and Health.

A picture of John F. McNamara, a New York City firefighter who died in 2009, is held at a media session in Washington last year. McNamara's widow believes exposure at the World Trade Center caused his cancer. (Alex Brandon/Associated Press)